The present invention relates to the field of the cyclic, torture testing of an engine cylinder head gasket. More particularly, the present invention relates to an apparatus and a method for rapidly cooling the engine, including the cylinder head and cylinders using the engine""s liquid cooling system, from a high temperature of approximately about 230xc2x0 F. to 250xc2x0 F. to a temperature of approximately about xe2x88x9216xc2x0 F. to xe2x88x9240xc2x0 F., thereby stressing the head gasket to between its extreme sealing limits.
Engine cylinder head gasket designs must be tested under extreme conditions to predict whether a particular design will be able to withstand a lifetime of rigors associated with the conditions to which it will be exposed in an engine during regular use. Tests are known for conducting torture tests of cylinder head gaskets for liquid cooled engines. In one type of test, the engine coolant in the engine is cycled between hot and cold under specific conditions for periods of time to cause the engine to expand and contract in a predetermined manner.
In this type of testing apparatus and method, the integrity of the engine""s head gasket and design are tested by cyclically exposing the engine to extreme coolant temperatures by running the engine hard to make it become very hot and then by running super chilled coolant in the engine""s cooling system, both for prolonged periods of time, thereby causing maximum expansion and contraction of the cylinder head, engine block, cylinder bolts, etc. and subsequent compression and relaxation of the head gasket. More specifically, the cylinder heads and cylinders are exposed to relatively high coolant temperatures of approximately about 230xc2x0 F. to 240xc2x0 F. and then relatively very cold or super chilled engine coolant is run into the testing system and engine so the engine is rapidly exposed to the very cold temperatures of about xe2x88x9240xc2x0 F. to xe2x88x9216xc2x0 F.
In fact, there is a known specification setting the parameters under which one OEM conducts such head gasket tests for engines. Ford Motor Company test specification CETP: 03.01-L315, details the timing, testing points, temperatures and methods for its preferred methodology in conducting head gasket torture testing, which is incorporated herein by reference. However, it is understood in practice that it is very difficult to develop a test apparatus which is capable of meeting every detail of this specification.
In one common test conducted pursuant to the Ford specification, the engine is exposed to the relatively hot engine coolant during a first test period and is then subsequently exposed to the relatively cold coolant in a second test period. During the first period, lasting on order about 15 minutes, the engine is started and stabilized at idle for 1 minute and as the first period continues the engine is then run at wide open throttle (W.O.T.) while yielding maximum horse power, and maximum internal cylinder pressures to stress the head gasket, for 14 minutes. During this first period the coolant out temperature commonly stabilizes between 230xc2x0 F. to 240xc2x0 F. and the coolant system pressure is on the order of approximately between 13 and 16 psig (90 to 110 kPa).
At the end of the first period, the engine is stopped (i.e., zero RPM) during the second test period for approximately 15 minutes. During the second test period, the relatively hot coolant is continuously replaced with super chilled coolant to maintain the coolant out temperature from the engine between approximately about xe2x88x9216xc2x0 F. to xe2x88x9240xc2x0 F. as quickly as possible, preferably within ten minutes of engine stoppage and remain at that level until fifteen minutes has passed since the engine stopped. The completion of the first and second test periods, completes one thirty minute test cycle. The test cycle is then continuously repeated until the engine cylinder gasket experiences a predetermined number of testing cycles (typically at least 50 or more testing cycles depending on the type of engine and customer requirements) or until the head gasket fails.
A conventional testing apparatus design for conducting a head gasket test for cooling the engine coolant to perform the second period of the testing cycle is shown in FIG. 1. Depending upon the engine size and type, a typical chill cycle (or second test period) requires 5 to 25 gallons per minute of super chilled coolant to reach the desired engine out cold temperature of approximately xe2x88x9216xc2x0 F. to xe2x88x9240xc2x0 F. Thus, for a 15 minute second test period, there will be required approximately between 75 and 375 gallons of super chilled engine coolant to complete one testing cycle. Since it is common for one cooling system to be designed to support several simultaneously running engine head gasket tests, the amount of required super chilled engine coolant may be doubled, tripled or even more. Thus, existing test facilities are known to begin with a 2000-3000 gallon insulated cold storage tank 20 containing a coolant 21 typically maintained between approximately xe2x88x9220xc2x0 F. and xe2x88x9240xc2x0 F.
It should be noted that the engine coolant can be any conventional or appropriate coolant or other liquid (or a combination thereof) that has a freezing point less than approximately xe2x88x9250xc2x0 F. Usually, it is common to use a 40/60 mixture of water and conventional coolant, such as an ethylene-glycol based coolant.
The tank 20 has an inlet 24, an outlet 26, and a vent 22. Super chilled coolant 21 exits the cold storage tank 20, via the outlet 26, and is pumped by a first vane or rotary pump 28 to a first valve 30. The coolant 21 entering the first valve 30 flows, via an inlet 32, into the cooling system of the engine 34 around the cylinder and cylinder head cooling cavities. While in the engine 34, the coolant 21 absorbs heat from the engine 34 thereby reducing the temperature of the engine 34 and its components. After passing through the engine 34, the coolant 21 exits, via an outlet 36, and flows to a second valve 38. At this juncture, the coolant 21 may be channeled into a air-cooled radiator 42 (via a radiator inlet 40) or be channeled into a recovery tank 48. It should be appreciated that the tank 48 must necessarily be of equal or greater size than storage tank 20.
Referring still to FIG. 1, if the coolant 21 is directed to the radiator 42, the coolant passes there through and exits the radiator 42 via an outlet 44. The coolant 21 then flows back to the first valve 30 which, in turn, directs the coolant 21 back to the engine 34. This is the typical valve selection and coolant flow for the hot cycle or the first test period wherein the coolant in the engine runs at a temperature of approximately about 230xc2x0 F. to 240xc2x0 F. On the other hand, if the coolant 21 exiting the engine 34 at the outlet 36 is pumped into an inlet 46 of the recovery tank 48, two possible results exist for the coolant 21.
The first result is that the heated engine coolant 21 may be channeled, via an outlet 36 in the recovery tank 48, into a refrigeration or super chilling unit 66 via an inlet 64 in the refrigeration unit 66. The refrigeration unit 66 is typically a relatively very large capacity system in the 30-100 ton range (wherein the system is capable of removing heat from the engine coolant at a rate of 360,000 to 1,200,000 BTU/Hr or 6,000 to 20,000 BTU/Min). The refrigeration unit 66 must be sufficiently large enough to rapidly cool the engine coolant 21 in the recovery tank 48 to the desired testing temperature while minimizing down time between cycles. The refrigeration unit 66 employs conventional mechanical cooling techniques such as using a hydrofluorocarbon refrigerant, or the like, to create a sufficient cooling capacity to super chill the engine coolant 21 to approximately xe2x88x9220xc2x0 F. to xe2x88x9240xc2x0F. (xe2x80x9ctesting temperaturexe2x80x9d) for use in conducting the head gasket test. Despite the significantly large cooling capability of the refrigeration unit 66, it is common to have the engine coolant 21 be circulated multiple times through the refrigeration unit 66 until the engine coolant 21 reaches the desired testing temperature. Once the desired testing temperature is reached, the re-cooled (and now super chilled) engine coolant 21 enters the recovery tank via a second inlet 52.
By circulating the re-cooled engine coolant 21 through the refrigeration unit 66 and outlet 68 back into the recovery tank 48, the overall temperature of the engine coolant 21 in the recovery tank 48 along with the pressure therein will be lowered. The recovery tank 48 is alternatively provided with a vent 50 to regulate pressure in the tank 48.
In the second result, the engine coolant 21 in the recovery tank 48 is not re-circulated through the refrigeration unit 66. Instead, the engine coolant 21 exits the recovery tank 48 via an outlet 54 and is pumped directly, by a third pump 60, back to the cold storage tank 20. This is typically done only if the coolant 21 is still at a sufficiently cold temperature within the testing temperature range for purposes of running the head gasket test.
It should also be appreciated that most, if not all, of the valves and controls of the present design are controlled by an electronic control system (not shown). It is known that the control system uses many known devices such as a Central Processing Unit (CPU) and other processing equipment to control the testing equipment and to operate the testing methodology. The control system (not shown), is employed to control the opening and closing of the first and second valves 30, 38 and to control the first, second, and third pumps 28, 72, 60. This known cooling system, as used for torture testing head gaskets, has experienced a number of problems which will be explained in detail.
To achieve the rapid cooling necessary to run the head gasket test within the limits of the noted specification, each test cycle conventionally uses approximately 75 to 375 gallons of engine coolant per test cycle, depending on engine size and type. Further, to be able to conduct multiple, continuous test cycles every 30 minutes, most installations must store roughly 2000 gallons or more of super chilled engine coolant thereby taking up a large amount of space and further adding to costs of an already expensive system. Further, the capital costs of assembling and installing the conventional system including the costs relating to the insulated cold storage tank 20, refrigeration system 66, and recovery tank 48 and the related network of tubes, conduits, pipes, controls, etc. are very significant. Accordingly, the cost to chill and store such relatively large volumes of engine coolant is great and makes running the head gasket test very expensive. However great the cost of the head gasket testing equipment, OEMs are forced to incur such costs because the warranty costs (several thousand dollars per vehicle) of having to repair faulty head gaskets are even far greater.
Second, the system is physically large and thereby occupies a large amount of floor space. In addition, the system employs a correspondingly large electrical infrastructure and the electrical energy costs are great with the above mentioned system since, it practice, it requires approximately 110 to 350 Kilowatts per hour to operate. This is primarily due to the fact that the large storage tank 20 has heat loss and requires constant refrigeration to keep the engine coolant 21 cold even when a test is not being conducted. Further, as a result of the overall size and complexity of the low temperature refrigeration system of the known art, frequent maintenance is required.
An alternative design has been proposed wherein engine coolant in the testing system is exposed to the direct injection of liquid nitrogen to reduce the temperature of engine coolant. However, this design has also been found to be problematic for a number of reasons and, in fact, can not be run in practice. As the liquid nitrogen is released directly into the engine coolant, the liquid nitrogen expands due to the warming effect of the engine coolant on the liquid nitrogen. The warming of the liquid nitrogen results in the release of massive amounts of gas since each gallon of liquid nitrogen used results in approximately 100 ft3 of gas produced. As a result, the system must be extensively ventilated to prevent a rapid pressure increase which could otherwise cause a system rupture. In addition, rapidly lowering the temperature of the engine coolant by direct exposure with liquid nitrogen causes significant freezing problems and has proven to be quite difficult to control on a continuous basis. In particular, the coolant often freezes at the injection point of the liquid nitrogen because the temperature of the liquid nitrogen is far below the freezing point of the engine coolant.
Additional attempts have been made to make direct expansion of liquid nitrogen with the coolant feasible. Such attempts include the use of high flow rate centrifugal pumps to rapidly pump the coolant through the system and avoid freezing of the coolant. However, these pumps have failed to solve the problem of engine coolant freezing, i.e., the engine coolant still frequently freezes in response to the direct application of liquid nitrogen due the difficulty in controlling such a process.
To avoid the rapid freezing caused by liquid nitrogen, some have tried using a highly pressurized brine. However, the highly pressured brine has also been found to be unsuccessful because the brine itself often freezes before it is able to sufficiently lower the temperature of the engine coolant.
In view of the above noted drawbacks with the existing systems, there remains a significant need to improve the known systems or to develop a system without the noted drawbacks. A new system is needed which can provide sufficient cooling effect to supply a sufficient amount of super chilled coolant to continuously run multiple and/or simultaneous head gasket torture tests while not experiencing the aforementioned problems and limitations of the known systems.
One embodiment of the present invention relates to a system and method of removing heat from engine coolant for use in conducting a torture test of a head gasket in an engine. Further, the present invention relates to a testing apparatus for use in rapidly and cyclically cooling the engine coolant that is circulated through the engine and thereby stressing the head gasket of the engine. In one embodiment of the present invention, the testing apparatus, for cooling the engine coolant circulated through the engine containing the head gasket to be tested, includes a heat exchanger utilizing liquid nitrogen for rapidly removing heat from the engine coolant, and a positive displacement pump in fluid communication with an outlet of the engine for pumping the engine coolant.
In one embodiment of the present invention, the testing apparatus, for cooling the engine coolant circulated through the engine containing the head gasket to be tested, includes a heat exchanger utilizing liquid nitrogen for rapidly removing heat from the engine coolant, a pump that is in fluid communication with an outlet of the engine for pumping the engine coolant, a valve in fluid communication with an outlet of the pump, and a liquid heat exchanger, for pre-cooling the engine coolant, having an inlet and an outlet. The liquid heat exchanger outlet is in fluid communication with the liquid nitrogen heat exchanger such that engine coolant passing through the liquid heat exchanger passes there through or may optionally be communicated directly to the engine. The valve is adapted to direct engine coolant flowing from the pump in a first direction if the temperature of the coolant is above a predetermined value and in a second direction if the temperature of the coolant is not above the predetermined value.
In one embodiment, the pump for circulating the engine coolant is a positive displacement pump which forces the engine coolant to flow at a relatively very high rate of approximately about sixty to approximately about eighty gallons per minute, relatively independent of the viscosity of the engine coolant. In one embodiment of the present invention, the testing apparatus includes a temperature measuring device adapted to measure the temperature of engine coolant passing through the positive displacement pump. In one embodiment, the testing apparatus of the present invention preferably includes less than about ten gallons of engine coolant adapted to flow through the cooling circuit of the engine and through the liquid heat exchanger and through the liquid nitrogen heat exchanger and back to the engine""s cooling circuit. The use of the liquid water heat exchanger provides for the pre-cooling of the engine coolant. In this regard, the use of a pre-cooler is more economical since the entire system uses less liquid nitrogen to cool the heated coolant generated during the hot cycle of the test. The liquid heat exchanger preferably removes sufficient heat from the engine coolant to change the temperature of the engine coolant leaving the engine from approximately 230xc2x0 F. to 240xc2x0 F. to approximately 110xc2x0 F. to 120xc2x0 F. The liquid heat exchanger preferably uses an approximately 60xc2x0 F. brine solution that is cooled as a result of the exhaust by-product of the liquid nitrogen heat exchanger (i.e., cold nitrogen gas). In one embodiment, the predetermined switchover point from using only the liquid heat exchanger to using both the liquid heat exchanger and the liquid nitrogen heat exchanger is preferably when the temperature of the engine coolant is in a range of approximately about 110xc2x0F. to about 120xc2x0 F. or more but may alternatively be selected at a point outside of the noted range.
In one embodiment, the head gasket testing apparatus includes a liquid nitrogen supply tank. In an alternative embodiment, the liquid nitrogen supply tank is located outside of a building and an intake line is provided in fluid communication between the liquid nitrogen supply tank and the liquid nitrogen heat exchanger.
In one embodiment of the present invention, the testing apparatus includes a liquid nitrogen heat exchanger including liquid nitrogen distribution manifold and at least one engine coolant heat exchanger adapted to have liquid nitrogen from the liquid nitrogen distribution manifold sprayed there upon. In one alternate embodiment, the liquid nitrogen heat exchanger includes a second engine coolant heat exchanger positioned with respect to the liquid nitrogen distribution manifold and adapted to have liquid nitrogen sprayed there upon to cool engine coolant passing through the engine coolant heat exchanger.
In one embodiment, the head gasket testing apparatus further includes a bypass loop adapted to circulate liquid nitrogen in the liquid nitrogen distribution manifold of the liquid nitrogen heat exchanger, to help in maintaining the liquid nitrogen within the liquid nitrogen distribution manifold at cryogenic temperatures to prevent liquid nitrogen vaporization (boiling) in the liquid nitrogen distribution manifold.
One embodiment of the present invention relates to a method of operating a testing apparatus for conducting a test of a head gasket in an engine. The method for operating the head gasket test apparatus includes the steps of running a first test period wherein the engine is running for a specified period of time under specified conditions and the temperature of engine coolant exiting the engine thereby rises to a certain engine out temperature range; stopping the engine for a period of time; pumping the heated engine coolant out of the engine; and measuring the temperature of the engine coolant exiting the engine to determine whether it is above a predetermined temperature. Further steps include, if the temperature of the engine coolant exiting the engine is above the predetermined temperature: then routing the engine coolant into a liquid heat exchanger to lower the temperature of the engine coolant; recycling the engine coolant back into the engine; and returning to the step of measuring the temperature of the engine coolant exiting the engine. In addition, the method of operating the head gasket test includes the step of: if the measured temperature of the engine coolant exiting the engine is below the predetermined temperature, directing the engine coolant into a liquid nitrogen heat exchanger to lower the temperature of the engine coolant to a temperature in the range of approximately xe2x88x9216xc2x0 F. to xe2x88x9240xc2x0 F.; recycling the engine coolant 21 back into the engine; and pumping the engine coolant out of the engine using the pump. In the one embodiment of the present invention, the method of operating the head gasket testing apparatus is repeated for one or more additional cycles or until the head gasket fails.
In one alternate embodiment, the invention includes a method of reducing the temperature of an engine coolant used in an automobile engine. The method of reducing the temperature of the coolant includes the steps of: pumping the engine coolant using a pump; and measuring the temperature of the engine coolant to determine whether its temperature at the point exiting the engine is above a predetermined temperature. If the temperature of the engine coolant is above the predetermined temperature, the method includes the step of using a positive displacement pump to pump the engine coolant through a liquid heat exchanger; using the positive displacement pump to pump the engine coolant through a liquid nitrogen heat exchanger; recycling the coolant back into the engine; and then repeating the process.
The method also includes the step of supplying liquid nitrogen to the liquid nitrogen heat exchanger from a supply tank. In one alternate embodiment, the method further includes the step of supplying liquid nitrogen to a bypass loop in the liquid nitrogen heat exchanger to ensure the liquid nitrogen in the liquid nitrogen heat exchanger does not boil. The method alternatively includes the step of venting gaseous nitrogen from the liquid nitrogen heat exchanger to an air-cooled radiator to work in lowering the brine temperature which was subsequently heated during the pre-cooling cycle in the liquid heat exchanger. In one embodiment, the method includes the step of maintaining the temperature of the engine coolant-at a second predetermined temperature of approximately about xe2x88x9240xc2x0 F. to approximately xe2x88x9216xc2x0F.
These and other features, aspects, and advantages of the present invention will become more apparent from the following description, appended claims, and accompanying exemplary embodiments shown in the drawings.